Load engaging members, such as forks, clamps, rods and the like are normally pivotally mounted on the carriage of a lift mast assembly. Typically, the load engaging member has a connecting end portion slidably and pivotally mounted on a horizontal shaft of the carriage. In some applications, for example rough terrain operation it is desirable to be able to pivot the fork about the shaft from a load engaging position, at which the fork extends forwardly from the carriage and the vehicle upon which the mast is mounted, to a transport position, at which the fork extends in a direction toward the vehicle. With the fork in the transport position the overall length of the vehicle is reduced. This permits the vehicle to be transported on a shorter truck bed, towed with a reduced turning radius and able to descend steep inclined ramps.
One problem encountered during transport of the lift trunk is inadvertent movement of the fork from the transport position to the load engaging position caused by bouncing of the vehicle, descending steep ramps, etc.
U.S. Pat. No. 3,825,139 dated July 23, 1974 to Warren P. Geis deals with this problem by providing a locking device which engages the fork and positively holds the fork in the transport position. This solution, however, has several deficiencies which the subject invention is directed to overcome.
Since the locking device positively supports the weight of the fork, the shear loads placed thereon during transport caused by fork bouncing will alternately cause failure of the locking device.
Also, the fork must be located at a specificed precise longitudinal position along the shaft in order to be engaged by the locking device. Due to the weight of the fork, this alignment is difficult to achieve and a substantial amount of time is wasted on the part of the operator.
Since the weight of the fork in the transport position tends to return the fork to the load engaging position the operator, during the locking operation, must support the weight of the fork at the time of engaging the lock. This is obviously a difficult task and requires a substantial amount of effort.
The present invention is directed to overcoming one or more of the problem as set forth above.